<?php
    $s0=1;
    $s1=4;
    $s2=8;
    echo "哈哈哈"."呵呵呵";
    echo "<br>";
    echo "$s1+$s2=" . ($s1+$s2);
    echo "<br>";
    echo "{$s1}+{$s2}=" . ($s1+$s2);
    echo "<br>";
    echo $s1+$s2;
    echo "<br>";
    echo "{$s2}减{$s1}等于4";
?>
